1. Field of the Invention
The present invention relates generally to sewing machinery and, more specifically, to an adjustment mechanism for a tongue of a button stitching machine.
2. Description of the Related Art
A button stitching machine is described in co-pending application, U.S. Ser. No. 07/362,244, filed June 6, 1989, now U.S. Pat. No. 5,058,515. One aspect of this machine is illustrated in FIG. 1 herein, whereby a tongue assembly 10 includes a rear tongue 12 and a lift-up tongue 14 which is pivotally mounted to the forward end of the rear tongue 12 so as to pivot upwardly about a horizontal pivot axis in the direction "B". The rear tongue 12 is mounted on a carriage 16 which is movably mounted on a support 18 so that the tongue assembly 10 can be moved between a rearward, inoperative position and a forward operative position. FIG. 1 illustrates the carriage and tongue assembly 10 in the forward operative position. In this position, a button 20 is stitched to a piece of fabric (not shown) which is folded around the end of the lift-up tongue 14. When the carriage and tongue assembly are in the operative position, the end of the lift-up tongue 14 is positioned such that a needle 22 enters or passes very closely to one of the slots 24 provided in the end of the lift-up tongue 14. Means for controlling and driving the needle 22 are schematically shown as control means 26. The control means 26 drives and controls vertical reciprocating movement of the needle 22 as it is passed from an upper needle bar 28 to a lower needle position (not shown), thereby reciprocating in the direction "C".
An additional drive and control means is schematically illustrated as control means 30 for moving the button 20 relative to a pressing member 32 during the stitching operation so that the needle thread 34 passes through the holes of the button 20. A foot 36 is either manually controlled or controlled by a control means 26 to press downwardly during the stitching operation thereby clamping the material being stitched against the top surface of the lift-up tongue 14. The foot is moved in the direction "F" in a conventional manner.
The rear tongue 12 is slidably connected to the carriage 16 by adjustment screws 38 which pass through slots 40 and are received in threaded bores (not shown) formed in the upper surface of the carriage 16. The slots 40 are elongated in the direction of sliding for the purpose of initial calibration of a position of the leading edge of the lift-up tongue in its operative position. Once the position of the leading edge of the tongue is initially calibrated, the screws 38 are tightened to lock the position of the leading edge of the lift-up tongue 14.
To facilitate the initial adjustment, an abutment screw 42 is provided in a mounting plate 44 which is mounted on the rear end 16a of the carriage 16. The abutment screw 42 has a threaded shaft portion 42a, a hex nut portion 42b, and a head portion 42c, all three portions being integrally formed. The end of the threaded shaft portion 42a abuts the end face 12a of the rear tongue 12. As shown in FIG. 1(a), if it becomes necessary to adjust the position of the rear tongue 12 forwardly, the two screws 38 are at first loosened by the operator with an appropriate tool. Then, the screw 42 is turned clockwise with either a screwdriver or by hand, if possible, so that the threaded portion 42a extending beyond the inner surface of the support plate 44 becomes longer by axially advancing the screw 42 as the screw rotates, thus pushing the rear tongue 12 forwardly.
The flat surfaces of the hex nut portion 42b are provided with numbers to indicate an adjusted position. The operator can then be told at what position the screw 42 should be turned to by indicating the number or other indicia which should appear on the uppermost flat surface of the hex nut portion 42b. The selected position is maintained by a leaf spring 46 mounted on a pintle 48 by means of a screw 50 so that as the screw 42 is turned, the leaf spring deflects downwardly until a surface of the hex nut portion is parallel to a normal position of the leaf spring 46. Once the operator sees that the adjustment number or other indicia is facing upwardly on the hex nut portion 42b, the screws 38 are then tightened to lock the position of the rearward tongue 12.
FIG. 1a shows the full-forward adjusted position of the rear tongue 12. The full-forward position is reached when the hex nut portion 42b abuts the outer surface of the support plate 44. To move the rear tongue 12 rearwardly, the screws 38 must be loosened again, and then the screw 42 is rotated counter clockwise (assuming a normal thread) to the desired adjusted position. However, when a rearward adjustment is made, since the end of the threaded portion 42a is not connected to the end face 12a of the rear tongue 12, the rear tongue 12 does not move rearwardly except until the operator pushes it rearwardly, usually after the screw 42 has been rotated to the desired adjusted position.
Thus, although the adjustment mechanism illustrated in FIGS. 1 and 1a provides an adequate means for making a fine adjustment of the position of the lift-up tongue 14, the adjustment mechanism requires at least one tool, i.e., a screwdriver for the adjustment screw 42 and screws 38. Moreover, two tools would be required if the screw 42 has a normal screw head but the screws 38 have a different head, such as a hex-socket. Moreover, since it is necessary for the operator to ensure that the screw 42 is always abutting the end face 12a at the rear tongue 12, there is always a possibility of operator error in tightening the screws 38 without such proper abutment as would be required.
In addition, because the hex nut portion 42b has six sides, there are only six discrete positions of adjustment for the screw, corresponding to only one complete rotation of the screw 42. Thus, the range of fine adjustment, and the positions in that range are somewhat limited.